The bivalve net is normally placed in seawater to catch pelagic spat of bivalves which are following the motion of the seawater, and which settle on a permanent growing place after some time, the permanent growing place consisting, in this case, of bivalve spat catching and farming facilities formed by one or more bivalve nets. Such bivalve collecting devices may be used for farming various kinds of bivalves, e.g. mussels.
In connection with known farming facilities for bivalves, it is common opinion and practice that the bivalves should be harvested and tended after their growing place, e.g. a rope or a strip of seine, with the farmed bivalves attached, has been brought ashore. Such an operation involves several drawbacks, many of the drawbacks being avoidable or reducible if harvesting and tending of the farmed bivalves, possibly cleaning of the bivalve collecting device could be carried out in water, and the present invention seeks to solve the technical challenges connected to harvesting and tending farmed bivalves and cleaning a bivalve net in water, preferably in seawater.
Known Technique
Devices for harvesting and tending bivalves in water, usually seawater, and cleaning associated bivalve net are known to a small degree.
In known forms of farming the bivalves are normally harvested and tended after the growing place with the attached farmed bivalves has been brought ashore.
Of such forms of farming the farming of bivalves may be mentioned, known i.a. from Japan, where for example small scallops are attached equally spaced along a great number of ropes hanging into the sea from floats, and nourish on prey in the form of micro-organisms and other nutrients floating past. The growing place, or the bivalve collecting device, may also simply consist of one or more ropes, either hanging vertically into the sea from above-lying floats, or hanging in a curve between two securing points near the water surface. Instead of rope(s), the bivalve collecting device may also be formed of one or more strips of seine (net resembling a fishing net). The attachment and growth area on the bivalve collecting device for the pelagic bivalve spat may be increased further through one or more ropes being passed through meshes of the net along each strip of seine. The use of fine-meshed seine as a bivalve collecting device has also been attempted.
Drawbacks of Known Technique
Harvesting and tending bivalves and cleaning the bivalve collecting device after they/it have/has been brought ashore is infested with a number of drawbacks. In good growing conditions bivalves normally grow fast and obtain a considerable weight and volume after some time. When the bivalves which are attached to one of more bivalve collecting devices in farming facilities, are to be lifted out of the water for harvesting or tending, the bivalve collecting device will be considerably heavier and more voluminous than when the bivalve collecting device was placed in the water. Therefore it may be relevant to dismantle the bivalve collecting device(s) into smaller units which are easier to handle, but still the work operation of bringing the complete bivalve collecting device, or units of it, with the attached bivalves ashore may require the use of heavy-duty lifting equipment and a relatively large loading area in order for the complete bivalve collecting device, or units thereof, to be laid down on a suitable vessel or device, e.g. a fish carrier. Besides, all lifting devices and load-carrying components of the bivalve collecting device must be formed and sized to withstand the final weight load applied to the bivalve collecting device when it is lifted out of the water, and the increasing weight load represented by the growing bivalves during the growing season in the water. After the bivalve collecting device with the attached bivalves has been brought out of the water, the bivalves are harvested and tended, possibly the bivalve collecting device is cleaned, often by hand, which is time-consuming work as the bivalves have often grown into bunches of bivalves, which will then have to be separated, and other organisms, e.g. starfish, and possible unwanted floating material, e.g. plastic bags and drift wood, must also be removed manually. Thus, there is a need for making some operations related to the farming of bivalves more efficient and automated to a greater extent.
Due to the small mesh width of the seine, the use of fine-meshed seine may have the effect that the farmed bivalves will grow tight together in a short time, so that water rich in oxygen and nutrients is prevented from flowing freely through the bivalve collecting device, and the farmed bivalves thereby will not have the required growing conditions.